Electromagnetic radiation (EMR) testing is presently hampered by reflections and resonances in the single testing chamber. Electromagnetic interference (EMI) from outside the chamber also occurs. A typical conventional test chamber can include a transmitter and antenna for directing electromagnetic radiation across a space toward a test specimen rotatably mounted. The rotatable specimen is normally moved to a test position and stopped for each test. Depending on the size of the specimen, such as a missile, tank, or other structure which may house equipment affected by EMR, such as electronic circuits, the space required for rotatably testing may be a limiting factor. For a missile, the longitudinal axis of the test specimen is positioned at some variable angle B with respect to the EMR propagation direction. This is done by support assembly and rotating table. Testing which must be done at outdoor, unshielded facilities are also subject to EMI.
The effect of impinging EMR on missile systems such as the guidance and control systems within a missile housing may be detected or maintained in several ways during testing. An antenna may be placed inside the test specimen housing to pick up the radiation pattern developed. This detected radiation may then be coupled out to monitoring detector equipment. Fiber optics may be utilized to monitor guidance and control telemetry to determine radiation effects. If the specimen is food to be cooked or involves a chemical curing process or sterilizing of equipment, a pickoff or detector is unnecessary.
Present EMR radiated susceptibility testing of electronic equipment is normally conducted in an electromagnetic shielded enclosure. The EMR is launched from an antenna to the test item but reflections in the enclosure (from the enclosure walls and other test support hardware) cause serious perturbation in the EMR fields. Chambers are lined with EMR absorbing material to reduce reflections. This material (sometimes referred to as anechoic) is expensive and partially effective.